1. Field of the Invention
The present invention relates to a rail assembly, and more particularly to a rail assembly for drawers.
2. Description of Related Art
A conventional rail assembly is widely used on drawers and generally includes an outer rail, an inner rail and an intermediate rail disposed between the outer rail and the inner rail. The outer rail is fixed to the desk. The inner rail is connected to the side of the drawer. Multiple steel balls are disposed between the intermediate rail and the inner rail such that the drawer pulls out or pushes in easily.
The conventional rail assembly further has a retrieving unit disposed on the bottom of the outer rail to provide an effort of automatic retraction for pushing the intermediate rail and the inner rail in the outer rail. However, the retrieving unit occupies the space of the outer rail. The length of the inner rail and that of the intermediate rail are shorter than that of the outer rail, otherwise the inner rail and the intermediate rail are not completely received in the outer rail. Therefore, the total travel (span) when the outer rail, the intermediate rail and the inner rail expand completely is less the ideal length (span), which is the triple length of the outer rail. If the actual travel (span) approaches to the ideal length (span), the pan ratio is good. Therefore, the short rail assembly has great expanding effort. The intermediate rail and the inner rail are not required to be shortened their length such that the strength of the intermediate rail and the inner rail are not affected. The conventional intermediate rail is cut for receiving a damping mechanism. The conventional rail assembly has a good travel (span) but a poor strength.
A conventional rail assembly in accordance with the prior art shown in FIG. 1 comprises an outer rail 90, an intermediate rail 91, an inner rail 92, a sliding rail 93, and a damper 94. The outer rail 90 has a U cut-shaped section. The outer rail 90 has a stopper 901 and a fixing base 902 disposed in a free end thereof. A sliding space 903 is defined between the outer rail 90 and the stopper 901 and the fixing base 902. The intermediate rail 91 has an opening 910 defined in one end thereof to prevent from interference with the sliding rail 93. The inner rail 92 is received in the sliding space 903 and movably slides relative to the outer rail 90. The inner rail 92 has a clasper 920 disposed in one end thereof and corresponding to the fixing base 902. The sliding rail 93 is fixed to the fixing base 902 and received in the sliding space 903 between the inner rail 92 and the fixing base 902 to form a closed type rail. When the intermediate rail 91 moves toward the fixing base 902, the sliding rail 93 is received in the opening 910. The sliding rail has a positioning hook 930 disposed therein and corresponding to the clasper 920. When the positioning hook 930 engages with the clasper 920, the inner rail 920 is connected to the sliding rail 93 in a predefined distance. The positioning hook 930 is limited by the closed type sliding rail 93. The damper 94 is disposed in the fixing base 902.
The opening 910 in the intermediate rail 91 results in the loss of the length and the strength. Besides, the fixing base 902 (inner rail 92) does not have any structure for fitting the inner rail 92 (opening 910). The inner rail 92 can not extend or retract efficiently. Therefore, the conventional rail assembly has the problem of poor span.
In other aspect, the damper 94 of the conventional rail assembly is disposed in the end of the outer rail 90. The damper 90 has an air chamber and a pushing rod. The pushing rod pushes the air chamber to create the effort of damping. The pushing rod occupies the space of the outer rail 90. When the inner rail 92 automatically retracts, the inner rail 92 abuts against the damper 94 to damp the inner rail 92. Therefore, the length of the inner rail 92 is limited such that the total travel (span) of the rail assembly is limited.
Furthermore, the adaptability between the retrieving unit and the outer rail is another problem. The conventional retrieving unit is used the inner wall of the outer rail as a rail. Therefore, the width of the retrieving unit is equal to that of the inner rail. For the outer rails with different sizes, the different retrieving units are required to fit the outer rails. This is not convenient for warehousing.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional rail assembly.